Comment # 4 on bug 931377 from Jon Grossart

More debugging:

installed patterns-openSUSE-gnome -- screen locked up after login from lightdm

set gdm as display server -- screen went to flickering between VT and black on
all terminals (booting into recovery complained about gnomeshell crashing)

booted 20150518 KDE Live CD -- screen locked up at black screen before desktop

booted 21050518 Gnome Live CD -- screen locked up before desktop

booted Kubuntu 15.04 Live CD -- worked fine, Plasma 5.2.x, no vboxvideo but
with mouse support

booted Kubuntu Wily Daily (2015-5-19) -- worked fine, Plasma 5.2.2, no
vboxvideo but with mouse support